What shows in your Task Manager>
Run TASKMGR -> Performance tab, push Resource Monitor button -> select Memory tab.
For example, on my 4GB 64-bit Windows 7 Pro system (ASUS P5Q3 board, P45 chipset, Intel Duo E8400 CPU, 2x2GB DDR3 memory, ATI HD4670 512MB GDDR3 video card:
Note that my ATI HD4670 512MB video card apparently does not take any memory from my 4GB physical memory, which is all available to Windows 7. RMB on Computer -> Properties shows my full 4GB installed, there is no second qualifying line showing "available... " (something less). And Resource Monitor also confirms that all 4GB is available for use by Windows 7 and programs.
I have a similar story on my other machine, with a 1GB ATI HD4850 card. Again, all 4GB is available. Nothing's been carved out for hardware use.